The present invention relates to continuous or near-continuous measurement of properties or constituents of body fluids, and particularly although not exclusively to measurement of blood glucose levels.
It is known to employ spectral analysis techniques to determine the concentration of constituents of the blood such as glucose concentrations. An example of such techniques is described in U.S. Pat. Nos. 5,222,496 and 4,979,509. Such systems generally operate through the skin, or are implanted. Systems which operate through the skin suffer from significant errors due to variations in properties of the skin not related to the constituents which are to be measured and due to relative movement between the sensor system and the skin and/or the underlying tissue.
Attempts at continuous, or near continuous, monitoring of blood glucose have been made for many years, as exemplified by U.S. Pat. Nos. 4,008,717 and 4,979,509. More recent attempts include U.S. Pat. No. 6,618,603.
There remains a need for a reliable, low-cost, disposable device which could provide minimally-invasive continuous or near-continuous monitoring of constituents of body fluids such as glucose.